1. Field of the Invention
The present invention relates to a cooling fan for a driving device and a cooling fan structure.
2. Description of the Related Art
Patent Document 1 proposes a cooling structure in which a cooling fan 10 is provided in a reduction machine 1 as illustrated in FIG. 7. The cooling fan 10 is integrally attached to an input shaft 2 (a rotary shaft) rotating at a high speed. The cooling fan 10 has a blade 12 and a rib 14. Rotation of the blade causes air movement. The rib 14 is arranged on the side of a reduction machine with respect to the blade 12 and integrally formed with the blade 12. The rib 14 causes the blade 12 to be fixed to the input shaft 2 via a cooling fan attaching member 16.
An angle of installing the blade 12 of the cooling fan 10 is parallel with an axis direction O (a tilt of the blade 12 with respect to the axis direction is zero). The reason why the angle of the blade 12 is zero is to match cooling capabilities of the cooling fan 10 in both rotational directions because the input shaft 2 of the reduction machine 1 may rotate in positive and negative rotations. Therefore, it is not easy to improve the cooling capability of the cooling fan 10 used for the reduction machine 1 in comparison with a case where the rotation direction is only one (single) such as an electric fan.
Practically, the cooling fan 10 illustrated in Patent Document 1 may be used together with a fan hood 8 as illustrated in FIG. 6. Said differently, a wind generated by the cooling fan 10 is sent to an outside of the input shaft 102 of the reduction machine 1 in radius directions of the input shaft 102 by the rotation of the cooling fan 10. The wind sent to the outside of the input shaft 102 of the reduction machine 1 in radius directions (an arrow W5) of the input shaft 102 hits an inside 8A of the fan hood 8 which is provided to cover the cooling fan 10. Then, the wind direction is changed to a direction indicated by an arrow W6. By the above structure, the cooling fan 10 is configured to send the wind to a mechanical section of the reduction machine even if the rotation direction of the cooling fan 10 is changed. The mechanical section includes a main body casing 106 other than the input shaft 102 and component parts of the reduction machine including a bearing casing 104.
[Patent Document 1] Japanese Laid-Open Patent Application No. 2003-322224
However, if the amount of the wind sent to the outside in the radius directions is sufficient to increase the wind speed, when the wind direction is changed by the fan hood 8, the wind amount and the wind speed are decreased. In addition, a distance d2 between the cooling fan 10 and the main body casing 106 is elongated, to thereby further reduce the wind amount and the wind speed when the wind reaches the main body casing 106 of the reduction machine. Therefore, it is difficult to obtain a sufficient cooling capability for the reduction machine 1 or the like with the example cooling fan 10, and therefore it is difficult to improve heat rating of the reduction machine 1 or the like. Further, it is possible to increase the size of the cooling fan 10 in order to improve the cooling capability. However, in this case, the size of an entire driving device including the fan hood may be excessively increased.
[Patent Document 1] Japanese Laid-Open Patent Application No. 2003-322224